1. Priority Claim
This application claims the benefit of priority from European Patent Application No. 11 165 443.0, filed May 10, 2011, which is incorporated by reference.
2. Technical Field
This invention relates to systems and methods for displaying three-dimensional landscapes, for example on displays of navigation systems.
3. Related Art
Navigation systems are used to guide a user to a destination. Usually, on a display of the navigation system the position of the navigation system may be shown with its surroundings. This may be done by showing the position on a map. However, often a three-dimensional perspective may be used, for example, the landscape surrounding the navigation system may be displayed in a three-dimensional manner.
One method for displaying such three-dimensional landscapes are so-called triangulated irregular networks. A triangulated irregular network (TIN) is a digital data structure used for the representation of a three-dimensional surface and may be made up of irregular distributed vertices, also referred to as nodes or mass points, and lines with three-dimensional coordinates, for example x, y, z, that are arranged in a network of non-overlapping triangles. TINs may be derived from altitude data of a rasterized digital altitude model.
A TIN therefore has a triangular network of vertices with associated coordinates in three dimensions as mentioned above which are connected by edges to form a triangular tessellation. Three-dimensional visualizations can then be created by rendering of the triangular facets. In regions where there may be little variation in surface height or altitude, the vertices may be widely spaced, whereas in areas of more intense variation of the altitude the vertices' density may be increased.
As explained above, between the vertices the altitude is interpolated, usually in a linear manner (for example, joining vertices by edges as described above constitutes such a linear interpolation). In some cases, this may lead to unnatural looking results. For example, if a river runs between two vertices, the river may be displayed with a slope in a direction perpendicular to its flowing direction, which does not exist for real rivers. Similar problems may occur with other landscape elements.